Bandar is in as much of a position to speak for more than a billion Sunnis as Daesh themselves. I'm not sure if you have the right idea of what Sunnis are, the Saudi government sure as shit isn't; that'd be like claiming Westboro Baptist Church goers are Christians.
Most Arab Sunnis despise Saudi Arabia far, far more than they do Iran or Shi'a people in general. Might come as a shock to some but most Muslims aren't brainless people who only live for their faith but actually follow the news and keep track of what's happening around them. Even if people didn't, the Saudi's racism towards anyone who's not from a Gulf state alone puts them up there with Israel and the US in terms of popularity.